docs: def load_conf_modules():
      """Load all modules that contain configuration.
  
      Method iterates over modules of :py:module:`monasca_persister.conf`
      and imports only those that contain following methods:
  
      - list_opts (required by oslo_config.genconfig)
      - register_opts (required by :py:currentmodule:)
  
      """
      for modname in _list_module_names():
          mod = importutils.import_module('monasca_persister.conf.' + modname)
          required_funcs = ['register_opts', 'list_opts']
          for func in required_funcs:
              if hasattr(mod, func):
                  yield mod